Interesting debate.
Most pop music in general uses the same 4 chords. The Axis of Awesome demonstrated this by mashing about 70 of them together, you can see it here.
http://www.youtube.com/watch?v=5pidokakU4I
However, I think there is a difference between "formula music" as you call it, and structure. Calling it formula music is a slap in the face. All music has some sort of structure to it. The only kind that doesn't is pure randomness and the argument could be made that that isn't music but rather just sound, or noise.
The Baroque period of music from the 1600s to 1750, was very mathematical in nature. J.S. Bach especially. The following Classical period had very rigid rules as to form, harmonic structure and such. The Romantic period brought with it more technically elaborate music, as well as chromatic harmonies all in the name of trying to be less structured and more emotional. Yet they could never escape structure completely.
The past century and this one has brought with it serialism, which is very formulated though in a different way, and chance music and randomness. The point here is that over the course of history, we have continually attempted to escape structure and the "rules" governing music. Yet as a society we end up right where we began. Because what is more popular today - the music of John Cage or the music of Lady Gaga? Yup...it's the music with the same 4 chords in it that we still listen to.
People love to pretend to be music connoisseurs but at the end of the day Nickelback still is one of the most artists around. Why? Because music in nature IS structured, it DOES have certain formulas....the formulas vary by genre and that's where our tastes differ....but we can't get away from formula music in general, because by in large, that's what music is. Some may have more basic, closed, rigid "formulas" to them (ie the same 4 chords) whereas other music is less rigid and more diverse, but all music is structured in one way or another.